Thanks Jatinah. Interesting, using magnetic flux to act like a storage capacitor. And yes, I'm familiar with dynamic braking on motors with magnets. I'm sure you can get dynamic braking with purely field and armature windings. But thanks again for taking the time to explain how this works. Now my knowledge base is just a little broader.

 

This helps to provide a sturdy motor movement and helps the motor with it's current needs. This is usually limited to DC motors as most AC motors take much less current.
, which is removing that "Magic FLUX" and disallowing it's buildup will hold a motor rotor rock still!
For fun, spin the motor with wires left loose....easy hey?
Now tie the red to the black and try to spin that same motor....not so easy? Have a great day!

Any motor that has either P.M. or powered field will produce a BEMF when in both powered and motoring mode, this BEMF is the same polarity as the supply, and opposes the applied voltage, if present, also the limiting factor for maximum RPM, and also one reason why a DC motor with a series field wound field will (can) operate in a run-away condition with the load removed.
Or a shunt wound-field motor will run away if the field is lost.
Max.
.

 

Hiya all and thank you for the interesting read . For the last few days all i been doing is reading up on mosfet's . H bridges's, pwm's etc and it's amazing how there is so much to know . I am doing as much research on this as i still would like to attempt to make one to drive my motor i just didn't want to run into a brick wall all the time . so learning as much as possible for now. Thank you Jatinah for your input as you rightly say "ti not all that easy to power a treadmill motor" i will re check the diode and fet and replace the cap and resistor to the value you have suggested and see what occurs . Thank you all again
Mal

 

Any motor that has either P.M. or powered field will produce a BEMF

What's a BEMF? I can guess that the EMF may be either Electro Motive Force or maybe Electro Magnetic Force. But I can't guess what the B may be. Can you explain?

Also, you mentioned "run-away condition" twice, once with the load removed and again with the field removed. My question is: "What?"

 

BEMF (Back Electro Motive Force) is the same polarity and a generated voltage that opposes the applied voltage, a DC motor with a shunt wound field can run away, sometimes to destruction if it loses its field when operating, hence large motors have field loss protection.
Series field motors like you have in your vacuum cleaner operate in a runaway condition due to gradually weakening field, they rely on load, windage, friction etc, to limit the rpm, this is the reason when you cover the intake on a vacuum (unload it) you can hear the RPM's go way up.
Max.

 

Vacuum cleaners don't rely on floor loading to stay in a safe region or they would fly apart when we lift them up, sure they increase speed, but they dont continue to speed up until the extremely high angular forces inside all rotating motors, would soon blow that contraption apart. I am not sure why Max keeps bringing up BEMF, it's a very tiny part of motor controls and designs but maybe he knows this subject well and it is not the same Polarity as the drive current, it is OPPOSING current to the normal drive function. BEMF would be a negative going spike on a positive rail.
BEMF is one of the reasons a vacuum motor doesn't continue to increase it's spin rate until shit flys apart, along with motor pole design and windings spacings. Basically put. Now in ALL "switched" motor controls, be they for DC or AC power rails for DC or AC motors respectfully(like in Treadmills), there are always considerations for BEMF which only rears it's ugly head during the FET off-time, when the motor is free wheeling, and acting like a generator. This free wheeling of a motor is a special time in the switching scheme(R-trr, Q of winding sets, drive frequency) when the BEMF is shunted, or basically drained off the switching line or yes, the BEMF pulse would travel back onto the source line and cause major issues, like smoke.
This BEMF opposing statement can confuse, as if one thinks of a heartrate signal on a scope at the hospital, they see an uptick, then downtick, repeat, repeat, repeat, ... the positive motor lead on a treadmill motor see's 165vDC, for some short slice of time, in the "microseconds range" or uSec, when the FET turns off, the free spinning generator now, shoots an opposing spike equal to the driving source back onto the + motor line for a short slice of time, and/or a positive going spike heading to the ground rail that would rip all logic circuits apart. Something called a KICKBACK (short for inductive kickback or "BEMF") DIODE begins to conduct that negative going spike of BEMF when the spike gets to .4vdc. This kickback diode will be found right next to the driving FET on a heatsink as it does a TON of work and gets roasty warm as does the FET. These powers being switched are lethal, and I have been doing this since 1976....I know lethal when I play with it...daily... it's quite a life, keep the questions going, learning for free can't be better~! Good Luck all.

 

I am not sure why Max keeps bringing up BEMF, it's a very tiny part of motor controls and designs but maybe he knows this subject well and it is not the same Polarity as the drive current, it is OPPOSING current to the normal drive function. BEMF would be a negative going spike on a positive rail.
l.

Forget any type of control for a moment, What do you suppose limits the current in a DC motor fed from a steady DC supply and also sets the maximum rpm?
Obviously you are not aware of the operation of wound field DC motor, either series field or shunt and the reason a series motor relies on friction etc to limit the rpm.
What explanation do you have of a shunt wound motor experiencing runaway to destruction when the field is lost? It is the same reason that a series motor operates to such a high RPM.
Also you agree, but do not explain why a universal (series) motor speeds up when the load is removed.
Max.

 

OK, here we go Max. All your posts about motors and folks questions result in your BEMF statements after statements. How would an untrained person use your BEMF statements and put that to rational use? Did these folks ask how to design the internals of a motor? How to measure or assume CEMF or BEMF?

Don't tell me what I don't know, maybe you'd like to list your diploma's....I will list mine....
USAF Precision Metrology Electronics Lab Specialist....52 week crush course, with 63% failure rates, graduated in top 10%
DeVry Institute of Technology, Kansas City, Mo., - 2yr Technician Degree, non-accredited back then.
Eastfield College Dallas, Tx., AAS Degree in Advanced Electronics majors in Power Distributions/Microelectronics
--extended 1yr for Advanced Physics and Heliophysics
Xerography, Irvine Calif., while designing for Brother Inc entities

Employers to date have included.....
Western Electric(turned into AT&T Microelectronics, Dallas Works), 5yrs, Engineering Technician, Hi-Speed ESS systems and Power
Power Clinic Inc, Dallas Texas, Power supplies/conditioners/inverters/single-to-3phase converters, Drives (AC/DC), control schemes
Motorola PCS Cellular, Harvard, ILL., Cellular design and production, CDMA,TDMA,Analog,Digital, Multi format, welsh-coding
Artesyn Communications Prod., Madison Wisc., Hi-Speed Gig+ Ethernet switchgear for Lucent & Others, see Katana750 Blades
Eaton Corporation, Watertown, Wisc., DRIVES, AC/DC, starters, intelligent relays, branch servicers/switches, industrial switchgear, crane drive controls, turbine generation controls, surface mount power products, intellignet motor controllers like the FP5000
http://www.eaton.com/Eaton/Products...utionRelays/CH-SeriesRelays/FP-5000/index.htm
Universal Electronics, Whitewater Wisc., Medical Products - FDA Approved rapid assembly facility....

Tell me again Max, where have you been bro? I don't simply speak it, I live it, design it, dream it, build it, proof it, and create for others.
Last idea I completed was for a local UW Madison Professor, who would like to measure "sound" via thermocouple faster than the human ear can catch it...as in....sound as ir-light travels at 186000mi/sec vs sound-waves at 768mi/hr so he would like to catch and graph sounds via ir......

So...maybe lets take a step back...this is who I am....these folks need real world help and discussions, not limited to one factor of the motor world, and trust me bro, I have sat thru more hours of class than most humans I currently know. Learning is critical for engineers, it begins when we start to walk, and ends when we do ;o) peace

 

I can see it is rather futile to continue with this discussion as my teachings in motor control appear to be at a variance with yours and your apparent attempts to answers so far.
Any answers given from here will be addressed to the OP.
Max.

 

Play nice you two.

MOST of the people who ask questions here (like myself) don't have the education and background others may have. When I contribute I do my best to be of help to the one asking the question. If I learn something along the way - good. But listing the lifetime awards and accolades one has achieved helps no one. In fact it only lessens the experience.

I don't need to know how long you've done what - where. I just need an answer to a question I asked. Most recently I asked about Op Amps. I've gotten a lot of good help and nobody has had to list their credentials. Makes this place a very warm and friendly place to ask and learn.

And for those who help others, I'm sure their reward is in knowing they helped someone learn something or solved someone's problem. I know it makes me feel good helping others. AND I appreciate when others help me.

It's OK to have a difference of opinion. And you can even say "I disagree with so-and-so" You can even say why you disagree. But there's no need to challenge anyone, that's not why we're here. So come on guys. Lighten up. Exactly why motors do what they do - that's not what this thread is about. The OP asked about a burned out resistor and blown away capacitor. Not about your degrees in advanced universe theory.

So play nice. Please.

 

Play nice you two.

Fair Enough...my apologies to all...the end ;o)

 

I got ERR - 5 on this board , What could be the problem? Plz Help

 

@arikly.arijit
Welcome to AAC.

If you have a question please post your own thread. At this point I don't know what you're asking aside from "What could be the problem?".

In crafting a question please be as complete and detailed as possible. If you have schematics please share them. If you're concerned about someone stealing an idea you may be working on - you are not obligated to be that specific or to provide a schematic. But if you want help then help us understand your problem fully. Someone here with vast knowledge will likely be proud to be of assistance.